1. Field of the Invention
This invention relates to a display apparatus which displays an image based on color data which are obtained by converting pixel data in a frame buffer by using a look-up table (hereinafter called "LUT").
2. Description of the Related Art
In a display apparatus currently known, a frame buffer stores pixel data for each pixel in a display screen, and outputs the pixel data as an address to an LUT disposed between the frame buffer and the image display so as to display a color graphic image by pixels having desired colors. Such a display apparatus is disclosed in Japanese Patent Laid-Open Publication 31184/1985.
To change the color of some pixels, color data whose addresses are designated by pixel data are usually overlaid with different color data in the LUT.
This method is advantageous in that the color can be changed instantly. However, if there are other pixels having the same pixel data in the frame buffer, the color of all the pixels having the same pixel data are changed simultaneously, thereby causing not only the desired area but also some undesired areas to be color-changed.
There is also known a method in which a color is changed by replacing pixel data in the frame buffer with pixel data of the newly desired color. This method is advantageous in that the color of only the desired area can be changed, but takes a lot of time to change the original color to the desired color or vice versa. In addition, an extra memory is required for storing the original color data temporarily. The second mentioned method is not so preferable for the above reasons.